[CMake] Macro's all and string expansion

[Brandon Van Every]

On 9/1/07, Tristan Carel <tristan.carel at gmail.com> wrote:
> Hi,
>
> While passing a regular expression to macro as parameter, I
> experimented strange behaviour:
>
> $ cat bar.cmake
> MACRO(FOO regexp)
>   IF("foo.bar" MATCHES "${regexp}")
>     MESSAGE(STATUS "FOO: match")
>   ENDIF("foo.bar" MATCHES "${regexp}")
> ENDMACRO(FOO)
>
> IF("foo.bar" MATCHES "foo\\.bar")
>   MESSAGE(STATUS "REFERENCE: OK")
> ENDIF("foo.bar" MATCHES "foo\\.bar")
>
> FOO("foo\\.bar")
> $
> $ /usr/bin/cmake --version
> cmake version 2.4-patch 6
> $
> $ cmake -P bar.cmake
> -- REFERENCE: OK
> CMake Error: Invalid escape sequence \.
> CMake Error: Syntax error in cmake code at
> /tmp/bar.cmake:11:
> syntax error, unexpected cal_ERROR, expecting $end (5), when parsing
> string "foo\.bar"
>
> I must increase the escape level to make the macro's call working:
>   FOO("foo\\\\.bar")
>
> I want to be able to pass non-tricky regular expressions to macros,
> firstly because escaping stuff is very annoying and secondly because a
> user shouldn't need to know macro's internal mechanisms to use it.
>
> If it is not a bug, can something clarify this to me?
> Thx by advance.

This is bug #5389, "MACRO consumes double escapes in string
arguments."  I discovered it for exactly the same regex processing
reasons you did.  It is very very annoying when trying to write more
abstract code.  A workaround is to pass variables instead of strings,
so that the macro argument reader can't ruin the strings.

Cheers,
Brandon Van Every